As is well known, punch presses are highly useful for producing various types of cutouts in sheet-like workpieces of metal, plastic, composite materials and the like. In recent years, numerically controlled punch presses have enabled the production of relatively complex cutouts by repetitive punch strokes in nibbling operations, because movement of a workpiece clamping mechanism may be controlled by an X-Y coordinate guidance system.
Moreover, with the advent of large turret assemblies in turret-type punch presses and with the later advent of automatic tool changer type punch presses, a fairly large amount of tooling may be provided within the press so that the operative punch and die may be readily changed. Thus, even complex configurations have been made possible through the optimization of computer numerically controlled systems in presses providing a multiplicity of interchangeable tools.
In most punch presses employing workpiece clamping elements which are moved by an X-Y coordinate system, there is some limitation as to areas of the workpiece which can not be subjected to the punching operation. In some instances, this will be caused by that portion of the workpiece necessarily occupied by the clamping elements; in others, by the interference that would result from the movement of the clamping elements against other portions of the press; in still others involving large workpieces, by the limitation in the total amount of movement of the clamping elements along the X-Y axes.
Generally, most machines utilize a guidance mechanism disposed adjacent the center piston of a C-shaped frame. These machines have a throat determined by the length of the spring between the rearmost position of the guidance and clamping mechanism and the punch work position. This throat distance generally limits the dimension of the workpiece.
Thus, it is sometimes necessary to release the clamping elements and then manually to move the workpiece so that it can be clamped again in a new orientation. In some instances, the clamping elements will merely be released and moved along the X axis to grip the workpiece at a point spaced from the original gripping position. When the workpiece released from clamping action, there is a potential for minor movement due to vibrations of the machine itself or ambient vibrations, and thus can cause substantial difficulties in producing a final product to precision tolerances.
On occasion, this will entail rotation of the workpiece 90.degree. or even 180.degree.. Obviously, such manual activity interrupts the automatic operation of the press by the computer control, increases the time required and cost and provides the potential for misalignment.
Recently there have been introduced punch presses which permit variation in the nature of the cutouts produced by rotation of the tooling may be coupled with the indexing of the workpiece to spaced positions to produce cutouts with the tooling rotated relative to the X and Y axes of movement of the workpiece so that the cutouts are at different angular relationships. The availability of such rotary action for the punch press tooling provided by these two rotary action presses has thus increased the versatility of a single set of tooling.
It is an object of the present invention to provide a novel punching method which enables the workpieces to be moved by the guidance system, rotated to a new orientation on the punch press base, and again clamped in the guidance system.
It is also an object to provide such a method in which the movement and reorientation are effected with precision and automatically.
Another object is to provide a novel punch press assembly which utilizes tooling that can be moved to clamp the workpiece and then to rotate the workpiece into a new orientation for gripping by the guidance and moving system.
A further object is to provide novel tooling for clamping and rotating a workpiece on a punch press.